The present invention relates generally to high temperature superconductors. More specifically, the present invention relates to Tl-Ba-Ce-Cu-O superconductors and processes for making same.
Tl-Ba-Cu-O and Tl-Ba-Ca-Cu-O superconducting systems have been identified. U.S. patent application Ser. No. 144,114 and Ser. No. 155,247, now U.S. Pat. No. 4,962,083, issued Oct. 9, 1990 filed in the name of Hermann and Sheng, two of the three inventors of the present invention, disclose, in part, Tl-Ba-Cu-O and Tl-Ba-Ca-Cu-O superconductor systems. The discovery of the Tl-Ba-Cu-O and Tl-Ba-Ca-Cu-O superconducting systems has led to the identification of a number of Tl-based superconducting compounds, including the series Tl.sub.m Ba.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.1.5m+2n+1, wherein m=1-2 and n=1-5.
One of the phases of the Tl-Ba-Ca-Cu-O system that has been identified is the Tl.sub.2 Ba.sub.2 Ca.sub.2 Cu.sub.3 O.sub.10 superconductor phase. This phase has a transition temperature of 125 K., which transition temperature, the inventors of the present invention believe, is the highest to date among existing high temperature superconductors.
The presently known phases of such high T.sub.c superconductors have a tetragonal structure and are p-type. These superconductive phases are also anisotropic. If a new superconductor system was discovered that had a different structure, it could be used for several special applications.